348
different acoustical events in a train of sounds—that is, rhythm represents a serial dura-
tional pattern—whereas metre involves a temporal invariance in terms of the regular
recurrence of pulses or beats marking off equal durational units, which can be organized
as measures. Metre therefore represents a more complex acoustical ‘gestalt’, since its per-
ception and production require information on sound intensity (accented and unaccented
events) and on periodicity of rhythmical events, the latter based on integration of inform-
ation over longer time periods. Again, by means of neuropsychological fractionation of
perceptive subfunctions in patients with brain lesions, it was possible to isolate neuronal
networks processing metre and rhythm, demonstrating spared metric judgement but dis-
rupted rhythmic discrimination.^7 It is beyond the scope of the present contribution to dis-
cuss the complex issue of local vs global gestalt processing in the auditory domain. Whereas
in the visual modality, a dissociation of neuronal substrates concerned with local (left pari-
etal) or global (right parietal) processing can clearly be demonstrated,^14 in the auditory
modality such a clear-cut neuroanatomical distinction is still under debate. This may be
related to the methodological problem of fractionating time structures in appropriate per-
ceptive units allowing for a clear and interindividually consistent discrimination between
local or global processing units. In fact, most experimental designs have not been very con-
vincing in excluding variable time fractionation based on rapidly changing individual
auditory habits.
‘Music centres’ in the brain reflecting the auditory biography
Although lesion studies conducted in larger groups of patients suffering from well-defined
lesions support the idea of modularity and hierarchy and yield relatively clear results, it still
remains a scientific challenge to further clarify the nature and function of these hypothes-
ized modules and hierarchies and to delineate their degree of autonomy and specificity to
music. Another, in our opinion, even more urgent problem arises when taking a look at the
individual data. In a recently published study,^15 where procedures were performed on
patients suffering from small unilateral ischemic lesions of the temporal, parietal, or frontal
lobe, respectively, a surprising heterogeneity of the patterns of impairment with respect to
modular subfunctions of auditory processing emerged. Whereas none of the patients had
a deficit in basic auditory perception as, for example, in pitch discrimination, in some indi-
viduals right hemispheric lesions produced deficits in more complex temporal or pitch
organization tasks, including in all instances, however, a combined deficit of local as well as
global processing stages. Following left hemispheric stroke, surprisingly dissociated impair-
ments of rhythm, metre, interval, or contour processing occurred, irrespective of whether
the lesion was localized anterior or posterior to the central sulcus. In summary, it emerged
that individually variable varieties of brain regions were necessary to ensure complex audit-
ory functions, including parts of the posterior parietal lobes and the frontal lobes. It there-
fore becomes evident that not only the temporal lobes, as suggested in the comprehensive
study of Liégois-Chauvel and co-workers,^13 but widespread and individually developed neur-
onal networks may underlie music processing. Without going into methodological details,
it should be mentioned in this context that our patients were investigated relatively early—
7–14 days following the ischemic stroke—before profound plastic changes compensating